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Abstract:

The invention relates to a method and device for expanding the travel or
control displacement of linear actuators that is available during an
imprinting or embossing stroke. The wedge error compensating head (2)
comprises a movable part (4), a stationary part (3) and at least three
linear actuators (8). Each linear actuator (8) is connected to one of the
parts (3, 4) at one end and to the other of the two parts (4, 3) by
wedges (9) at the other end. By means of the wedges (9), it is possible
to coarsely or roughly compensate for wedge errors and possible
tolerances of individual subcomponents of the system. The linear
actuators (8) are only used for fine or precision compensation for the
wedge error. In this way, sufficient control displacement is available
for the imprinting stroke with the linear actuators.

Claims:

1. A wedge error compensating head (2) in particular for imprinting or
embossing a substrate (5) and for carrying out an active wedge error
compensation, comprising: a stationary part (3) and a part (4) being
movable relative thereto; and at least three linear actuators (8) between
the two parts (3 and 4), wherein displaceable wedges (9) are provided
between the linear actuators (8) and the movable part (4) or the
stationary part (3).

2. The wedge error compensating head (2) according to claim 1, wherein
the wedges (9) are integrated in the movable part (4) or in the
stationary part (3) of the wedge error compensating head (2).

3. The wedge error compensating head (2) according to claim 1, wherein
the movable part (4) can be connected with a mask (6) or a substrate (5).

4. The wedge error compensating head (2) according to claim 1, wherein
each linear actuator (8) comprises a piezo element.

5. The wedge error compensating head (2) according to claim 1, comprising
a pneumatic or hydraulic means for individually moving the wedges (9).

6. The wedge error compensating head (2) according to claim 1, comprising
a controller for individually controlling or regulating the movement of
the individual wedges (9).

7. The wedge error compensating head (2) according to claim 1, comprising
at least three measuring probes (15) or at least three sensors (13) for
measuring the position of the movable part (4) of the wedge error
compensating head (2).

8. The wedge error compensating head (2) according to claim 1, comprising
a plurality of brakes (7) for locking the position of the movable part
(4) of the wedge error compensating head (2).

9. A device for imprinting or embossing a substrate (5) by means of a
wedge error compensating head (2) according to claim 1.

10. A method for actively compensating for a wedge error by using a wedge
error compensating head (2) according to claim 1, comprising the steps
of: (a) carrying out a coarse adjustment of the wedge error compensation
by means of the wedges (9); and (b) carrying out a fine adjustment of the
wedge error compensation by means of the linear actuators (8).

11. The method according to claim 10, comprising steps (a1) to (a8)
within step (a) and step (b1) within step (b): (a1) moving the wedge
error compensating head (2) against a mask (6) or a substrate (5); (a2)
measuring the position of the movable part (4) of the wedge error
compensating head (2) by means of measuring probes (15) or sensors (13);
(a3) locking the angle between the wedge error compensating head (2),
possibly with substrate (5) or mask (6), and the mask (6) or the
substrate (5) by applying brakes (7); (a4) removing the wedge error
compensating head (2) from the mask (6) or the substrate (5); (a5)
positioning the wedges (9) between the linear actuators (8) and the
movable part (4) of the wedge error compensating head (2); (a6)
connecting the movable part (4) of the wedge error compensating head (2)
with the wedges (9) and contacting the linear actuators (8) with the
wedges (9); (a7) opening the brakes (7); (a8) checking the position of
the movable part (4) of the wedge error compensating head (2) by means of
the measuring probes (15) or the sensors (13) and accordingly aligning
the wedges (9); and (b1) actively compensating for the wedge error by
means of the linear actuators (8) and the position of the movable part
(4) of the wedge error compensating head (2) measured in step (a2).

Description:

FIELD OF THE INVENTION

[0001] The invention relates to a method and a device for wedge error
compensation, and in particular to a method and a device in which the
control displacement available for the wedge error compensation can be
increased.

BACKGROUND TO THE INVENTION

[0002] When producing micro-electronic, micro-optical and micro-mechanical
components, structures are transferred to a substrate by means of a mask
or a punch by using embossing or imprint lithography. If the angle
between the plane of the mask and the plane of the substrate changes, the
structures are no longer uniformly imprinted in the substrate. This
situation is referred to as wedge error. Therefore, wedge error
compensation substantially determines the quality of the imprint.

[0004] In passive wedge error compensation, the wedge error compensating
head moves with or without the substrate against the mask or punch. It
contacts the mask either with its entire surface or via spacers. After
the movable part of the wedge error compensating head or the substrate
has contacted the mask, the relative position of the mask and the movable
part of the wedge error compensating head is locked by applying brakes.
The angle formed between the plane of the mask and the plane of the
substrate or the surface of the movable part of the wedge error
compensating head is maintained for at least one process cycle.

[0005] A problem related with passive wedge error compensation is that the
brakes can hold a relatively small force of about 100 N only. For SUSS
MicroTec Microlens Imprint Lithography (SMILE®), Substrate Conformal
Imprint Lithography (SCIL) and Nanoimprint Lithography (NIL) processes
this force is too small.

[0006] In order to overcome the disadvantages of passive wedge error
compensation, active wedge error compensation is used. Active wedge error
compensation first takes place in a manner equal to that of passive wedge
error compensation. Instead of locking the relative position of the mask
relative to the movable part of the wedge error compensating head or the
substrate, measuring probes are used for referencing this relative
position. Then, the movable part of the wedge error compensating head is
placed onto three linear actuators arranged in the reference plane, e.g.
at azimuthal intervals of 120° . By means of the measuring probes
and by applying the linear actuators, it is possible to actively
compensate for the wedge error. If piezo elements are used for the linear
actuators, typically displacements of up to 80 μm can be compensated
for. In this connection, the control displacement is the maximally
available distance by which a linear actuator can move the movable part
relative to the stationary part of the wedge error compensating head.

[0007] A problem related with this active wedge error compensation is the
small control displacement, in particular if, e.g., piezo elements are
used for the linear actuators. In a compact system, the available
constructional space is limited. Therefore, the piezo elements cannot be
elongated in order to increase the control displacement. The control
displacements available for the actual imprinting stroke are reduced
further if the maximally available control displacements are already
necessary to a large extent for a tolerance compensation for the
dimensions of the components used in the system, e.g. the chuck, the
adapter frame, the mask holder, the substrate holder, etc. It can even be
the case that only a few micrometers are left for the actual imprinting
stroke.

[0008] In view of the above-mentioned problems of the prior art, it is an
object of the present invention to provide a method and a device in which
the control displacement available for the wedge error compensation is
increased. It is a further object of the invention to be able to use the
control displacement of the linear actuators almost completely for the
imprinting stroke. These objects are achieved by the features of the
claims.

SUMMARY OF THE INVENTION

[0009] In achieving these objects, the invention starts out from the basic
idea that the tolerances of the components used in the system and of the
substrate are previously coarse-compensated for, e.g., by using wedges,
so that only a small part, e.g., 10% of the control displacement of the
linear actuators is necessary for the remaining fine wedge error
compensation. The remaining control displacement of the linear actuators
can thus be used almost completely for the imprinting stroke for
processing the substrate.

[0010] The wedge error compensating head for compensating for the wedge
error comprises a stationary part, a movable part and linear actuators.
The movable part is connected with the stationary part through the linear
actuators. One end of each linear actuator is connected directly with one
of the two parts of the wedge error compensating head or abuts against
the counter bearing of the respective part of the wedge error
compensating head. Between the other end of each linear actuator and the
other part of the wedge error compensating head, a coarse compensation is
made, e.g., by inserting wedges. Preferably, three linear actuators are
used, which are arranged symmetrically in the reference plane, e.g., at
azimuthal intervals of 120° . Thus, the movable part of the wedge
error compensating head can be positioned as desired relative to the
stationary part of the wedge error compensating head.

[0011] The wedges allow a coarse compensation for tolerances of the
components of the system including the substrate. For example, in case of
a non-uniformly thick substrate in which the thickness decreases from one
edge to the other edge, the movable part of the wedge error compensating
head can be aligned such by means of the wedges that the substrate is
almost parallel to a mask for imprinting structures into the substrate.
By means of the linear actuators, a fine correction of the parallelism of
substrate and mask can then be made, and finally the imprinting stroke
for structuring the substrate can be carried out by uniformly applying
all linear actuators.

[0012] For achieving a compact design of the device, the wedges can be
integrated in the movable part or in the stationary part of the wedge
error compensating head. The movable part of the wedge error compensating
head can be used for receiving the substrate. In this case, the movable
part of the wedge error compensating head with the substrate is pressed
against a stationary mask in order to imprint structures into the
substrate. Alternatively, the mask can be arranged on the movable part of
the wedge error compensating head, so that upon application of the linear
actuators, the mask is pressed against the stationary substrate to
perform the imprinting operation.

[0013] The linear actuators preferably comprise piezo elements. The
deflection of the linear actuators or the deflection of the wedges takes
place individually for each linear actuator or for each wedge,
respectively, by means of a controller. The wedges are deflected, i.e.
displaced preferably pneumatically.

[0014] In accordance with an embodiment, the linear actuators are highly
precise and have in particular only small ranges of operation (control
displacements also in the nm range).

[0015] By means of measuring probes provided on a stationary holder for
receiving the mask or the substrate and contacting the surface of the
movable part, the position of the movable part of the wedge error
compensating head can be measured relative to this holder. Alternatively,
other sensors can be used. These sensors measure the position of sensor
pins mounted on the movable part of the wedge error compensating head.
Preferably, at least three of these measuring probes or sensors are used.

[0016] By using brakes, the position of the movable part of the wedge
error compensating head can be locked relative to the stationary part of
the wedge error compensating head.

[0017] Alternatively, the wedges are not aligned actively to compensate
for the wedge error. In this case, only after aligning and locking the
movable part of the wedge error compensating means, the wedges are moved
between the linear actuators and a part of the wedge error compensating
head in order to fill the gaps. In this way, too, a coarse compensation
for the wedge error is achieved. After releasing the brakes, only a
slight control displacement of the linear actuators is necessary for
carrying out the fine wedge error compensation.

[0018] The wedge error compensation according to the present invention can
be described as follows: First, the wedge error, which is caused by
tolerances of the components used in the system including the substrate,
is coarse-compensated for by positioning the wedges. Then, a possibly
still present slight wedge error is fine-compensated for by means of the
linear actuators. Therefore, almost the maximum control displacement of
the linear actuators is still available in the subsequent imprinting
stroke.

[0019] In detail, the wedge error compensation according to the present
invention can be carried out as follows: First, the wedge error
compensating head or its movable part is pressed against a mask arranged
in a stationary holder, so that the position of the movable part of the
wedge error compensating head can be determined in this position. By
applying brakes, the angle between the mask and the surface of the wedge
error compensating head or of the substrate on the wedge error
compensating head is locked. Subsequently, the wedge error compensating
head or the movable part of the wedge error compensating head is moved
away from the mask. Then, the wedges are moved between the linear
actuators and the movable part of the wedge error compensating head.
Subsequently, the brakes are opened. By checking the position of the
movable part of the wedge error compensating head by means of the
measuring probes or the sensors, the wedges can be accordingly
readjusted. However, this readjustment of the wedges can also be omitted.
Now, the coarse adjustment of the position of the movable part of the
wedge error compensating head is finished. Subsequently, the position of
the movable part of the wedge error compensating head is fine-adjusted by
means of the linear actuators. Since the control displacement of the
linear actuators was not necessary for the coarse compensation for the
wedge error and possible tolerances, after the fine compensation for the
wedge error, almost the entire control displacement of the linear
actuators is still available for the imprinting stroke.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the following, the invention will be described in more detail
with reference to the drawings in which:

[0021] FIG. 1 shows a sectional view of a wedge error compensating device
before measurement of the position of the movable part of the wedge error
compensating head (reference measurement),

[0023] FIG. 3 shows a sectional view of the wedge error compensating
device after measurement of and compensation for the wedge error and
before the imprinting stroke.

DETAILED DESCRIPTION OF THE INVENTION

[0024] FIG. 1 shows a sectional view of a device for active wedge error
compensation. The device is suitable for imprinting structures into a
substrate 5. The device comprises the wedge error compensating head 2
according to the invention and a holder 1 to which a mask (or punch) 6 is
fixed for imprinting the structures into the substrate 5.

[0025] The wedge error compensating head 2 comprises a movable part 4 and
a stationary part 3. Pressure springs 14 are provided between the movable
part 4 and the stationary part 3. By using a hydraulically or
pneumatically operating means 17, the movable part 4 and the non-movable
part 3 can be moved towards each other in that a piston 19, which is
fixed to the movable part 4, is moved towards the stationary part 3 by a
negative pressure in the means 17 located in the stationary part 3. By
means of the brakes 7, the movable part 4 can be locked relative to the
stationary part 3. The substrate 5 to be treated is applied to the free
surface of the wedge error compensating head 2.

[0026] The movable part 4 of the wedge error compensating head 2 is
moreover connected via linear actuators 8 with the stationary part 3 of
the wedge error compensating head 2. On one end, the linear actuators are
connected directly with the stationary part of the wedge error
compensating head 2. A support element 16 is provided on the other end of
the linear actuators 8. Wedges 9 can be moved in channels K provided for
this purpose, so that a contact between support element 16 and wedge 9,
on the one hand, and wedge 9 and movable part 4, on the other hand, can
be achieved. FIG. 1 shows two linear actuators 8. Preferably, the wedge
error compensating head 2 comprises three linear actuators 8, which are
arranged symmetrically at azimuthal intervals of 120° (as seen in
the imprinting direction Z). Moreover, the linear actuators 8 preferably
comprise piezo elements. A simultaneous deflection of all actuators 8
causes the imprinting stroke which presses the movable part 4 of the
wedge error compensating head 2 with the substrate 5 onto the mask 6.

[0027] In addition to the mask 6, also spacers 18 are attached to the
holder 1. The spacers 18 can be inserted between mask 6 and substrate 5.

[0028] The device according to FIG. 1 moreover comprises measuring probes
15. The measuring probes 15 are connected with measuring heads 12 through
bores in the holder 1. The measuring heads 12 detect the movement or
position of the measuring probes 15 and provide a corresponding signal to
a controller (not shown). By means of its free ends or tips, the
measuring probes can contact the surface of the movable part 4 of the
wedge error compensating head in order to determine the position of the
movable part 4. Preferably, at least three measuring probes 15, which are
offset in the azimuth direction relative to the imprinting axis Z by
120° each and comprise corresponding measuring heads 12, are used
in order to be able to measure the position of the movable part 4
precisely in the plane.

[0029] A sensor 13 is provided in the stationary part 3 of the wedge error
compensating head 2 for determining the movement or position of a sensor
pin 11 fixed to the movable part 4 of the wedge error compensating head
2. Preferably, at least three pairs of a sensor 13 and a sensor pin 11
are used, which are offset in the azimuth direction relative to the
imprinting axis Z by 120° each. The sensors 13 and sensor pins 11
offer a further possibility for measuring the position of the movable
part 4 of the wedge error compensating head 2.

[0030] The entire wedge error compensating head 2 can be moved via a
lifting means 20 in the imprinting direction Z. For example, it is
necessary to move the wedge error compensating head 2 by the lifting
means 20 far away from the holder 1 in order to change the substrate 5
and/or the mask 6.

[0031] FIG. 2 shows a sectional view of the wedge error compensating
device while measuring the position of the movable part 4 of the wedge
error compensating head 2. For being able to later compensate for a wedge
error, first a reference measurement must be carried out. It must be
determined in which position of the movable part 4 of the wedge error
compensating head 2 the angle between substrate 5 and mask 6 is minimal,
i.e. when the two elements are aligned optimally parallel. For this
purpose, spacers 18 can be inserted between substrate 5 and mask 6. Then,
the movable part 4 is moved so far in the direction of the mask 6 until
the spacers 18 contact both the substrate 5 and the mask 6.

[0032] By means of the measuring probes 15 or sensors 13, the reference
measurement is carried out. Alternatively, the reference measurement can
also be carried out without spacers 18 in that the mask 6 and the
substrate 5 are brought in direct contact.

[0033] FIG. 2 shows that after the reference measurement the wedges 9 are
moved so far within the channels K provided for this purpose that the
wedges 9 contact both the movable part 4 and the support elements 16. The
wedges 9 are moved pneumatically by means of the connections 10 for
pressurized air.

[0034] FIG. 3 shows the device according to the invention after removal of
the spacers 18. The wedge error and the tolerances of the component used
in the system, including the substrate 5, have already been
coarse-compensated for by the wedges 9. The wedge error is
fine-compensated for by use of the linear actuators 8. Since the coarse
compensation has already been carried out, only slight control
displacements of the linear actuators 8 are necessary for the fine
compensation. For example, only about 10% of the maximally available
control displacement of a linear actuator 8 are necessary for the fine
compensation. Therefore, about 90% of the maximum control displacement of
the linear actuators 8 are still available for the subsequent embossing
or imprinting stroke.

[0035] In the following, a possible sequence of steps of a wedge error
compensation according to the invention is described:

[0036] In step 1 it is first checked whether the wedges are in their basic
position. If they are not in the basic position, they are brought in the
basic position. The basic position is the position in which the wedges 9,
as shown in FIG. 1, are in an outer position far away from the linear
actuators 8.

[0037] In step 2, the wedge error compensating head 2 is moved against a
mask 6, so that the substrate 5 or the movable part 4 is aligned parallel
to the mask 6.

[0038] In step 3, the position of the movable part 4 of the wedge error
compensating head 2 is measured. This reference measurement is necessary
for being able to realign the movable part 4 of the wedge error
compensating head 2 in this exact position before imprinting.

[0039] In step 4, the angle between the substrate 5 or the movable part 4
of the wedge error compensating head 2 and the mask 6 is locked by
applying brakes.

[0040] In step 5, the wedge error compensating head 2 moves away from the
mask 6.

[0041] In step 6, the wedges 9 are clamped by moving them between the
linear actuators 8 and the movable part 4 of the wedge error compensating
head 2.

[0042] In step 7, the movable part 4 of the wedge error compensating head
2 is drawn by the piston 19 of the means 17 onto the linear actuators 8.

[0043] In step 8, the brakes 7 are opened. Thus, the position of the
movable part 4 of the wedge error compensating head 2 is determined by
the position of the wedges 9.

[0044] In step 9, the position of the wedges 9 can be checked and
improved.

[0045] In step 10, the wedge error is actively fine-compensated for by
means of the linear actuators 8. The position of the movable part 4 of
the wedge error compensating head 2 measured in step 3 is used as
reference position.

[0046] Then the device is ready for an imprinting stroke in the Z
direction by synchronously controlling the linear actuators 8.

[0047] Above, the invention has been explained on the basis of a mask 6
with stationary holder 1 and the substrate 5 being on the movable part 4.
Alternatively to the representation in FIGS. 1 to 3, in accordance with
the invention the mask 6 can also be arranged on the movable part 4 of
the wedge error compensating head 2, wherein in this case the substrate 5
is accordingly fixed to the holder 1.

[0048] Moreover, it has been explained above that the wedges 9 can be
actively displaced in order to perform the coarse wedge error
compensation as exactly as possible. Alternatively, only after measuring
the reference position and locking the movable part 4 of the wedge error
compensating head 2, the displaceable wedges are moved only once between
the linear actuators 8 and a part of the wedge error compensating head.
The wedges can already contact the linear actuators 8 and the
corresponding part of the wedge error compensating head, but without
leading to a change in the position of the involved elements.
Alternatively, the wedge is moved only so far that there is no contact
between wedge and linear actuator 8 or the corresponding part of the
wedge error compensating head. This control displacement of the wedge can
be monitored, e.g., by means of a suitable sensor. After the wedge has
been positioned, the brakes are released. Because of the positioning of
the wedges, the wedge error has already been coarse-compensated for. For
the fine wedge error compensation, only a slight control displacement of
the linear actuators is necessary.

[0049] Alternatively, tensile springs can be used instead of the pressure
springs 14. In this case, tensile springs are arranged between the
movable part 4 and the stationary part 3. In this case, the movable part
4 and the non-movable part 3 can be moved away from each other by using a
hydraulically or pneumatically operating means 17 in that a piston 19,
which is fixed to the movable part 4, is moved away from the stationary
part 3 by a positive pressure in the means 17 located in the stationary
part 3.

Patent applications by Sven Hansen, Garching DE

Patent applications in class WITH MEASURING, TESTING, OR INSPECTING

Patent applications in all subclasses WITH MEASURING, TESTING, OR INSPECTING